A crew member aboard the International Space Station took this photo of a 15-kilometer (9.5-mile) section of Pangong Lake (Pangong Tso) on the western end of the Tibetan Plateau. In total, the lake extends 134 kilometers (83 miles) and spans the international border between India and China. The lake is one of the highest in the world, at an elevation of 4,225 meters (13,862 feet).

In this winter scene, a sheet of cracked ice tops part of the lake (right side of the image). On the left side, open water appears blue. Shallow water offshore of a delta, formed by a small, winding river, appears green.

Parallel lines along the coastlines of bays are visible in the high-resolution version of this image. These lines indicate raised beaches, which formed in the past when lake levels were higher.

Several roads cut across the landscape, including one with switchbacks that ascends a steep slope. These roads facilitate tourist travel from both India and China. During the summer, species such as bar-headed geese and Brahminy ducks attract bird watchers to the lake, which is a major breeding ground for migrating birds.

Astronaut photograph ISS070-E-80680 was acquired on January 25, 2024, with a Nikon D5 digital camera using a focal length of 1150 millimeters. It is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The image was taken by a member of the Expedition 70 crew. The image has been cropped and enhanced to improve contrast, and lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by Justin Wilkinson, Texas State University, JETS Contract at NASA-JSC.

It’s May and it’s getting warm (in the Northern Hemisphere). At a time like this, the Eta Aquarid meteor shower is a great excuse to look up at the night sky.

This year’s shower peaks close to the new moon — the opposite of a full moon — which is ideal. Dark skies mean better viewing conditions, which will come as a relief to anyone who tried to catch this show last year when a dazzling full moon filled the sky with light, making meteor viewing next to impossible. These conditions also contrast nicely with the Lyrid meteor shower last month, during which a nearly full waxing gibbous moon may have ruined your attempt to make a wish on a shooting star.

When to watch the Eta Aquarids in 2024

The Eta Aquarids produce a long show, with activity from April 15 to May 27 this year. However, if you’re only looking up once, plan to do it during the show’s period of peak activity on the night of May 4 and into the wee hours of the morning on May 5. In theory, 2 a.m. local time is the absolute best time (due to factors we’ll get into below), but meteors don’t follow rules, so the hours between 2 a.m. and dawn are sure to be exciting as well.

Past experience with this shower indicates that the Eta Aquarids come in bursts. This means if you look up during a lull, you might think you’ve missed the show. But wait a while, and  there won’t be any ambiguity; these are fast meteors, and you’ll generally know from the pace of the action that you’re seeing the Eta Aquarids. Patience will be rewarded.

How do I see the Eta Aquarids?

Since most Mashable readers are in the Northern Hemisphere, the unfortunate answer to this question is: for best results, switch hemispheres. Southern Hemisphere-based stargazers are blessed with a 50 meteor-per-hour spectacle (assuming conditions are ideal), while northerners can only hope to see 10-30 per hour. Honestly, however, 10-30 is still good.

Find a patch of dark sky located above an area far from cities and towns. A wide open view is best, so if you’re reading this from the bottom of a well, catching a meteor shower is going to be challenging. Get comfortable. Stay warm. Preserve your night vision by not looking at your phone.

What are the Eta Aquarids anyway? 

The Eta Aquarids get their name from their radiant point which is, in simple terms, the place in the sky where the meteors originate. The Eta Aquarids originate in the constellation Aquarius, so timing your viewing of the meteors involves waiting for Aquarius to rise above the horizon (which is why waiting until 2 a.m. local time is your best bet). But Aquarius is a collection of stars light-years away, and the meteors themselves are as little as 31 miles away when we see them burning up in our atmosphere. 

Generally speaking, meteor showers are the result of the Earth passing through a comet’s trail of tiny dust and ice particles. The Eta Aquarids’ happen to have a celebrity parent: the Michael Jordan of space rocks, Halley’s Comet. The most famous comet in the solar system won’t visit Earth’s vicinity for decades, but this shower is our annual encounter with the lingering evidence of its existence. 

Can apps help me find the Eta Aquarids?

Stargazing apps like Sky Safari are highly recommended for stargazing in general, but they aren’t very useful during meteor showers. An app can make it a breeze to find Aquarius, but the bright screen will make meteors harder to see, and they streak across the entire sky anyway, rather than clustering around their radiant point. 

The best advice is: just look up, and wait.

Last November, NASA’s Lucy mission conducted a flyby of the asteroid Dinkinish, one of the Main Belt asteroids it will investigate as it makes its way to Jupiter. In the process, the spacecraft spotted a small moonlet orbiting the larger asteroid, now named Selam (aka. “Lucy’s baby”). The moonlet’s name, an Ethiopian name that means “peace,” pays homage to the ancient human remains dubbed “Lucy” (or Dinkinish) that were unearthed in Ethiopia in 1974. Using novel statistical calculations based on how the two bodies orbit each other, a Cornell-led research team estimates that the moonlet is only 2-3 million years old.

The research was led by Colby Merrill, a graduate student from the Department of Mechanical and Aerospace Engineering at Cornell. He was joined by Alexia Kubas, a researcher from the Department of Astronomy at Cornell; Alex J. Meyer, a Ph.D. student at the UC Boulder College of Engineering & Applied Science; and Sabina D. Raducan, a Postdoctoral Researcher at the University of Bern. Their paper, “Age of (152830) Dinkinesh-Selam Constrained by Secular Tidal-BYORP Theory,” recently appeared on April 19th in Astronomy & Astrophysics.

Merrill was also part of the NASA Double Asteroid Redirection Test (DART) mission, which collided with the moonlet Dimorphos on September 26th, 2022. As part of the Lucy mission, Merrill was surprised to discover that Dinkinesh was also a binary asteroid when the spacecraft flew past it on November 1st, 2023. They were also fascinated to learn that the small moonlet was a “contact binary,” consisting of two lobes that are piles of rubble that became stuck together long ago.

While astronomers have observed contact binaries before – a good example is the KBO Arrokoth that the New Horizons spacecraft flew past on January 1st, 2019 – this is the first time one has been observed orbiting a larger asteroid. Along with Kubas, the two began modeling the system as part of their studies at Cornell to determine the age of the moonlet. Their results agreed with one performed by the Lucy mission based on an analysis of surface craters, the more traditional method for estimating the age of asteroids. As Merrill said in a recent Cornell Chronicle release:

“Finding the ages of asteroids is important to understanding them, and this one is remarkably young when compared to the age of the Solar System, meaning it formed somewhat recently. Obtaining the age of this one body can help us to understand the population as a whole.”

Binary asteroids are a subject of fascination to astronomers because of the complex dynamics that go into creating them. On the one hand, there are the gravitational forces working on them that cause them to bulge and lose energy. At the same time, binary systems will also experience what is known as the Binary Yarkovsky–O’Keefe–Radzievskii–Paddack (BYORP) effect, where exposure to solar radiation alters the rotation rate of the bodies. Eventually, these forces will balance out and reach a state of equilibrium for the system.

For their study, Merril and his team assumed that Selam formed from material ejected from Dinkinesh before the BYORP effect slowed its rotation down. They also assumed that the system had since reached a state of equilibrium and that the density of both objects was comparable. They then integrated asteroid data obtained by the Lucy mission to calculate how long it would take Selam to reach its current state. After performing about 1 million calculations with varying parameters, they obtained a median age estimate of 3 million years old, with 2 million being the most likely result.

This new method complements the previous age estimates of the Lucy mission and has several advantages. As their paper indicates, this method can yield age estimates based on asteroid dynamics alone and does not require close-up images taken by spacecraft. It could also be more accurate where asteroid surfaces experienced recent changes and can be applied to the moonlets of other known binary systems, which account for 15% of near-Earth asteroids (NEAs). This includes Didymos and Dimorphos, which are even younger.

The researchers hope to apply their new method to this and other binary systems where the dynamics are well-characterized, even without close flybys. Said Kubas:

“Used in tandem with crater counting, this method could help better constrain a system’s age. If we use two methods and they agree with each other, we can be more confident that we’re getting a meaningful age that describes the current state of the system.”

Further Reading: Cornell Chronicle