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By European Space Agency
From its vantage point outside Earth’s atmosphere, more than 36 000 km above Earth’s surface, the Copernicus Sentinel-4 mission will detect major air pollutants over Europe in unprecedented detail. It will observe how they vary on an hourly basis – a real breakthrough for air quality forecasting.
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By NASA
2 Min Read June’s Night Sky Notes: Seasons of the Solar System
Two views of the planet Uranus appear side-by-side for comparison. At the top, left corner of the left image is a two-line label. The top line reads Uranus November 9, 2014. The bottoms line reads HST WFC3/UVIS. At the top, left corner of the right image is the label November 9, 2022. At the left, bottom corner of each image is a small, horizontal, white line. In both panels, over this line is the value 25,400 miles. Below the line is the value 40,800 kilometers. At the top, right corner of the right image are three, colored labels representing the color filters used to make these pictures. Located on three separate lines, these are F467M in blue, F547M in green, and F485M in red. On the bottom, right corner of the right image are compass arrows showing north toward the top and east toward the left. Credits:
NASA by Kat Troche of the Astronomical Society of the Pacific
Here on Earth, we undergo a changing of seasons every three months. But what about the rest of the Solar System? What does a sunny day on Mars look like? How long would a winter on Neptune be? Let’s take a tour of some other planets and ask ourselves what seasons might look like there.
Martian Autumn
Although Mars and Earth have nearly identical axial tilts, a year on Mars lasts 687 Earth days (nearly 2 Earth years) due to its average distance of 142 million miles from the Sun, making it late autumn on the red planet. This distance and a thin atmosphere make it less than perfect sweater weather. A recent weather report from Gale Crater boasted a high of -18 degrees Fahrenheit for the week of May 20, 2025.
Credit: NASA/JPL-Caltech Seven Years of Summer
Saturn has a 27-degree tilt, very similar to the 25-degree tilt of Mars and the 23-degree tilt of Earth. But that is where the similarities end. With a 29-year orbit, a single season on the ringed planet lasts seven years. While we can’t experience a Saturnian season, we can observe a ring plane crossing here on Earth instead. The most recent plane crossing took place in March 2025, allowing us to see Saturn’s rings ‘disappear’ from view.
A Lifetime of Spring
NASA Hubble Space Telescope observations in August 2002 show that Neptune’s brightness has increased significantly since 1996. The rise is due to an increase in the amount of clouds observed in the planet’s southern hemisphere. These increases may be due to seasonal changes caused by a variation in solar heating. Because Neptune’s rotation axis is inclined 29 degrees to its orbital plane, it is subject to seasonal solar heating during its 164.8-year orbit of the Sun. This seasonal variation is 900 times smaller than experienced by Earth because Neptune is much farther from the Sun. The rate of seasonal change also is much slower because Neptune takes 165 years to orbit the Sun. So, springtime in the southern hemisphere will last for several decades! Remarkably, this is evidence that Neptune is responding to the weak radiation from the Sun. These images were taken in visible and near-infrared light by Hubble’s Wide Field and Planetary Camera 2. Credit: NASA, L. Sromovsky, and P. Fry (University of Wisconsin-Madison) Even further away from the Sun, each season on Neptune lasts over 40 years. Although changes are slower and less dramatic than on Earth, scientists have observed seasonal activity in Neptune’s atmosphere. These images were taken between 1996 and 2002 with the Hubble Space Telescope, with brightness in the southern hemisphere indicating seasonal change.
As we welcome summer here on Earth, you can build a Suntrack model that helps demonstrate the path the Sun takes through the sky during the seasons. You can find even more fun activities and resources like this model on NASA’s Wavelength and Energy activity.
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By NASA
2 min read
Space Cloud Watch Needs Your Photos of Night-Shining Clouds
Noctilucent Clouds observed from Bozeman, MT on 16 July 2009 at 4:29 MDT. The Space Cloud Watch project needs more photos like this one to diagnose changes in our atmosphere! Photo credit: Dr. Joseph A Shaw Noctilucent or night-shining clouds are rare, high-altitude clouds that glow with a blue silvery hue at dusk or dawn when the sun shines on them from below the horizon. These ice clouds typically occur near the north and south poles but are increasingly being reported at mid- and low latitudes. Observing them helps scientists better understand how human activities may affect our atmosphere.
Now, the Space Cloud Watch project is asking you to report your own observations of noctilucent clouds and upload your own photographs. Combined with satellite data and model simulations, your data can help us figure out why these noctilucent clouds are suddenly appearing at mid-low latitudes, where temperatures are usually too warm for them to form.
“I find these clouds fascinating and can’t wait to see the amazing pictures,” said project lead Dr. Chihoko Cullens from the University of Colorado, Boulder Laboratory for Atmospheric and Space Physics.
Did you see or photograph any night-shining clouds? Upload them here. Later, the science team will transfer them to a site on the Zooniverse platform where you or other volunteers can help examine them and identify wave structures in the cloud images.
If you love clouds, NASA has more citizen science projects for you. Try Cloudspotting on Mars, Cloudspotting on Mars: Shapes, or GLOBE Observer Clouds!
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Last Updated May 15, 2025 Related Terms
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By NASA
4 min read
May’s Night Sky Notes: How Do We Find Exoplanets?
Astronomers have been trying to discover evidence that worlds exist around stars other than our Sun since the 19th century. By the mid-1990s, technology finally caught up with the desire for discovery and led to the first discovery of a planet orbiting another sun-like star, Pegasi 51b. Why did it take so long to discover these distant worlds, and what techniques do astronomers use to find them?
The Transit Method
A planet passing in front of its parent star creates a drop in the star’s apparent brightness, called a transit. Exoplanet Watch participants can look for transits in data from ground-based telescopes, helping scientists refine measurements of the length of a planet’s orbit around its star. Credit: NASA’s Ames Research Center One of the most famous exoplanet detection methods is the transit method, used by Kepler and other observatories. When a planet crosses in front of its host star, the light from the star dips slightly in brightness. Scientists can confirm a planet orbits its host star by repeatedly detecting these incredibly tiny dips in brightness using sensitive instruments. If you can imagine trying to detect the dip in light from a massive searchlight when an ant crosses in front of it, at a distance of tens of miles away, you can begin to see how difficult it can be to spot a planet from light-years away! Another drawback to the transit method is that the distant solar system must be at a favorable angle to our point of view here on Earth – if the distant system’s angle is just slightly askew, there will be no transits. Even in our solar system, a transit is very rare. For example, there were two transits of Venus visible across our Sun from Earth in this century. But the next time Venus transits the Sun as seen from Earth will be in the year 2117 – more than a century from the 2012 transit, even though Venus will have completed nearly 150 orbits around the Sun by then!
The Wobble Method
As a planet orbits a star, the star wobbles. This causes a change in the appearance of the star’s spectrum called Doppler shift. Because the change in wavelength is directly related to relative speed, astronomers can use Doppler shift to calculate exactly how fast an object is moving toward or away from us. Astronomers can also track the Doppler shift of a star over time to estimate the mass of the planet orbiting it. NASA, ESA, CSA, Leah Hustak (STScI) Spotting the Doppler shift of a star’s spectra was used to find Pegasi 51b, the first planet detected around a Sun-like star. This technique is called the radial velocity or “wobble” method. Astronomers split up the visible light emitted by a star into a rainbow. These spectra, and gaps between the normally smooth bands of light, help determine the elements that make up the star. However, if there is a planet orbiting the star, it causes the star to wobble ever so slightly back and forth. This will, in turn, cause the lines within the spectra to shift ever so slightly towards the blue and red ends of the spectrum as the star wobbles slightly away and towards us. This is caused by the blue and red shifts of the star’s light. By carefully measuring the amount of shift in the star’s spectra, astronomers can determine the size of the object pulling on the host star and if the companion is indeed a planet. By tracking the variation in this periodic shift of the spectra, they can also determine the time it takes the planet to orbit its parent star.
Direct Imaging
Finally, exoplanets can be revealed by directly imaging them, such as this image of four planets found orbiting the star HR 8799! Space telescopes use instruments called coronagraphs to block the bright light from the host star and capture the dim light from planets. The Hubble Space Telescope has captured images of giant planets orbiting a few nearby systems, and the James Webb Space Telescope has only improved on these observations by uncovering more details, such as the colors and spectra of exoplanet atmospheres, temperatures, detecting potential exomoons, and even scanning atmospheres for potential biosignatures!
NASA’s James Webb Space Telescope has provided the clearest look in the infrared yet at the iconic multi-planet system HR 8799. The closest planet to the star, HR 8799 e, orbits 1.5 billion miles from its star, which in our solar system would be located between the orbit of Saturn and Neptune. The furthest, HR 8799 b, orbits around 6.3 billion miles from the star, more than twice Neptune’s orbital distance. Colors are applied to filters from Webb’s NIRCam (Near-Infrared Camera), revealing their intrinsic differences. A star symbol marks the location of the host star HR 8799, whose light has been blocked by the coronagraph. In this image, the color blue is assigned to 4.1 micron light, green to 4.3 micron light, and red to the 4.6 micron light. NASA, ESA, CSA, STScI, W. Balmer (JHU), L. Pueyo (STScI), M. Perrin (STScI) You can find more information and activities on NASA’s Exoplanets page, such as the Eyes on Exoplanets browser-based program, The Exoplaneteers, and some of the latest exoplanet news. Lastly, you can find more resources in our News & Resources section, including a clever demo on how astronomers use the wobble method to detect planets!
The future of exoplanet discovery is only just beginning, promising rich rewards in humanity’s understanding of our place in the Universe, where we are from, and if there is life elsewhere in our cosmos.
Originally posted by Dave Prosper: July 2015
Last Updated by Kat Troche: April 2025
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By NASA
3 Min Read March’s Night Sky Notes: Messier Madness
Showing a large portion of M66, this Hubble photo is a composite of images obtained at visible and infrared wavelengths. The images have been combined to represent the real colors of the galaxy. Credits:
NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; Acknowledgment: Davide De Martin and Robert Gendler by Kat Troche of the Astronomical Society of the Pacific
What Are Messier Objects?
During the 18th century, astronomer and comet hunter Charles Messier wanted to distinguish the ‘faint fuzzies’ he observed from any potential new comets. As a result, Messier cataloged 110 objects in the night sky, ranging from star clusters to galaxies to nebulae. These items are designated by the letter ‘M’ and a number. For example, the Orion Nebula is Messier 42 or M42, and the Pleiades are Messier 45 or M45. These are among the brightest ‘faint fuzzies’ we can see with modest backyard telescopes and some even with our eyes.
Stargazers can catalog these items on evenings closest to the new moon. Some even go as far as having “Messier Marathons,” setting up their telescopes and binoculars in the darkest skies available to them, from sundown to sunrise, to catch as many as possible. Here are some items to look for this season:
M44 in Cancer and M65 and 66 in Leo can be seen high in the evening sky 60 minutes after sunset. Stellarium Web Messier 44 in Cancer: The Beehive Cluster, also known as Praesepe, is an open star cluster in the heart of the Cancer constellation. Use Pollux in Gemini and Regulus in Leo as guide stars. A pair of binoculars is enough to view this and other open star clusters. If you have a telescope handy, pay a visit two of the three galaxies that form the Leo Triplet – M65 and M66. These items can be seen one hour after sunset in dark skies.
Locate M3 and M87 rising in the east after midnight. Stellarium Web Messier 3 Canes Venatici: M3 is a globular cluster of 500,000 stars. Through a telescope, this object looks like a fuzzy sparkly ball. You can resolve this cluster in an 8-inch telescope in moderate dark skies. You can find this star cluster by using the star Arcturus in the Boötes constellation as a guide.
Messier 87 in Virgo: Located just outside of Markarian’s Chain, M87 is an elliptical galaxy that can be spotted during the late evening hours. While it is not possible to view the supermassive black hole at the core of this galaxy, you can see M87 and several other Messier-labeled galaxies in the Virgo Cluster using a medium-sized telescope.
Locate M76 and M31 setting in the west, 60 minutes after sunset. Stellarium Web Plan Ahead
When gearing up for a long stargazing session, there are several things to remember, such as equipment, location, and provisions:
Do you have enough layers to be outdoors for several hours? You would be surprised how cold it can get when sitting or standing still behind a telescope! Are your batteries fully charged? If your telescope runs on power, be sure to charge everything before you leave home and pack any additional batteries for your cell phone. Most people use their mobile devices for astronomy apps, so their batteries may deplete faster. Cold weather can also impact battery life. Determine the apparent magnitude of what you are trying to see and the limiting magnitude of your night sky. You can learn more about apparent and limiting magnitudes with our Check Your Sky Quality with Orion article. When choosing a location to observe from, select an area you are familiar with and bring some friends! You can also connect with your local astronomy club to see if they are hosting any Messier Marathons. It’s always great to share the stars! You can see all 110 items and their locations with NASA’s Explore the Night Sky interactive map and the Hubble Messier Catalog, objects that have been imaged by the Hubble Space Telescope.
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