Study Findings: No Certainty of a Milky Way–Andromeda Collision

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Image (Credit): The Andromeda galaxy, or M31, spans 260,000 light-years across. (NASA/JPL-Caltech)

Nature Astronomy abstract of the study findings:

It is commonly believed that our own Milky Way is on a collision course with the neighbouring Andromeda galaxy. As a result of their merger, predicted in around 5 billion years, the two large spiral galaxies that define the present Local Group would form a new elliptical galaxy. Here we consider the latest and most accurate observations by the Gaia and Hubble space telescopes, along with recent consensus mass estimates, to derive possible future scenarios and identify the main sources of uncertainty in the evolution of the Local Group over the next 10 billion years. We found that the next most massive Local Group member galaxies—namely, M33 and the Large Magellanic Cloud—distinctly and radically affect the Milky Way–Andromeda orbit. Although including M33 increases the merger probability, the orbit of the Large Magellanic Cloud runs perpendicular to the Milky Way–Andromeda orbit and makes their merger less probable. In the full system, we found that uncertainties in the present positions, motions and masses of all galaxies leave room for drastically different outcomes and a probability of close to 50% that there will be no Milky Way–Andromeda merger during the next 10 billion years. Based on the best available data, the fate of our Galaxy is still completely open.

Citation: Sawala, T., Delhomelle, J., Deason, A.J. et al. No certainty of a Milky Way–Andromeda collision. Nat Astron (2025).
https://doi.org/10.1038/s41550-025-02563-1

Study-related stories:

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Pic of the Week: Barred Spiral Galaxy NGC 5335

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Image (Credit): Barred Spiral Galaxy NGC 5335 (NASA, ESA, STScI)

This week’s image looks like something ginned up by AI, but it is from the Hubble Space Telescope. Just the number of stray galaxies in the image is amazing.

Here is the description of the image from the European Space Agency’s (ESA) Hubble page:

Barred spiral galaxy NGC 5335 observed by the Hubble Space Telescope takes up the majority of the view. At its center is a milky yellow, flattened oval that extends bottom left to top. Within the oval is a bright central region that looks circular, with the very center the brightest. In the bright central region is what looks like a bar, extending from top left to bottom right. Around this is a thick swath of blue stars speckled with white regions. Multiple arms wrap up and around in a counterclockwise direction, becoming fainter the farther out they are. Both the white core and the spiral arms are intertwined with dark streaks of dust. The background of space is black. Thousands of distant galaxies in an array of colors are speckled throughout.

Trump Administration Proposes 25 Percent Cut to NASA’s Budget

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It should come as no surprise at this point that NASA will fall victim to massive budget cuts like so many other civilian agencies. While it will not disappear like the US Agency for International Development, it will be severely wounded as the result of a proposed 25 percent cut to its budget.

The White House’s proposed 2026 budget is setting aside $7 billion for the Moon missions and $1 billion for Mars missions, but it seems just about everything else is up for grabs. For instance, we would see the show shutdown of the Space Launch System rocket and the Orion spacecraft so they could become fully commercial. In addition, the orbiting lunar Gateway will be cut completely.

Specifically, the budget summary states:

The Budget phases out the grossly expensive and delayed Space Launch System (SLS) rocket and Orion capsule after three flights. SLS alone costs $4 billion per launch and is 140 percent over budget. The Budget funds a program to replace SLS and Orion flights to the Moon with more cost-effective commercial systems that would support more ambitious subsequent lunar missions. The Budget also proposes to terminate the Gateway, a small lunar space station in development with international partners, which would have been used to support future SLS and Orion missions.

Moreover, the Mars funding would not cover the sample return mission. Hence, SpaceX might get a boost to head towards Mars while we are stranding samples that help us to understand why we might want to go to Mars. We will also see the end of the Nancy Grace Roman Space Telescope, pruning back the accomplishments we have made since the Hubble Space Telescope to make the universe more available to scientists and the public.

If we ignore the future of the Artemis mission for a moment, a NASA press release boasted about all the events over the past 100 days to prepare for the Artemis mission. This is a hopeful sign that the Moon mission is still vital and viable at the moment, even with the defunding efforts underway. However, given some of the recent failures of the private sector efforts to reach the Moon, and the continual delays in SpaceX’s Starship, the future for Moon missions after the SLS does not look too promising at the moment.

The future also looks somewhat bleak when you look at proposed cuts to NASA’s funding for space science, space technology, and STEM programs. The endless faith in the private sector forgets the benefits of a government supporting and nudging these efforts.

As Casey Dreier, Chief of Space Policy for The Planetary Society, clearly stated:

These cuts would cause irreparable losses, throwing away billions of dollars invested by the U.S. taxpayers in productive space hardware and infrastructure. Space science is a critical national investment that engages our cutting edge economic, scientific, and educational abilities across the country.

Pic of the Week: Happy Birthday Hubble!

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Image (Credit): The Hubble Space Telescope in low-Earth orbit. (NASA)

This year marks the 35th anniversary of the Hubble Space Telescope. It was launched on April 24, 1990 aboard the Space Shuttle Discovery. The telescope was expected to have a service life of 35 years, though it is still going strong with various proposals to update the telescope and keep it operating for years to come.

To mark the occasion, NASA put together a video highlighting missions and related images. The celebration will continue throughout the year with new images and other selected items.

Here are a few interesting facts related to the Hubble:

  • Hubble is currently located 326 miles (525 km) above Earth’s surface. If you could drive straight up, you could reach it in about the same time it would take you to drive from Baltimore, Maryland to Boston, Massachusetts. 
  • Hubble races through its orbit at about 17,000 miles per hour (27,000 kph), completing an orbit about every 95 minutes. That means it sees 15 sunrises every day.
  • While Hubble is speeding around Earth, it can lock onto a target without deviating more than 7/1000th of an arcsecond, or about the width of a human hair seen at a distance of one mile.
Image (Credit): Hubble 35th Anniversary Graphic. (NASA)

Podcast: The Curious Universe

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If you are looking for new podcast material, you may want to check out NASA’s Curious Universe podcast. It has been around for a while, but it is starting a new series celebrating Earth from April 15 to May 13.

The first episode in the new Earth series is titled “How NASA Sees Our Blue Marble.” In the episode, we hear from Karen St. Germain, the director of NASA’s Earth Science Division. It is a chance to learn about the planet that NASA spends the most time studying.

If you like this series, you can go back and listen to other episodes, such as:

-“Inside the Team That Keeps Hubble Flying” (March 14, 2025)
-“The Sun Series” (March 19 to May 3, 2024)
-“Defending the Planet from Asteroids” (February 21, 2023)
-“The Search For Life: Are We Alone?” (June 21, 2022)