The most amazing thing about light is that it takes time to travel through space. Because of that one simple fact, when we look up at the Universe we see not a snapshot but a history. The photons we capture with our telescopes tell us about their journey. This is particularly true when gravity comes into play, since gravity bends and distorts the path of light. In a recent study, a team shows us how we might use this fact to better study black holes.
Placing a mass driver on the Moon has long been a dream of space exploration enthusiasts. It would open up so many possibilities for the exploration of our solar system and the possibility of actually living in space. Gerard O’Neill, in his work on the gigantic cylinders that now bear his name, mentioned using a lunar mass driver as the source of the material to build them. So far, we have yet to see such an engineering wonder in the real world, but as more research is done on the topic, more and more feasible paths seem to be opening up to its potential implementation.
Massive stars about eight times more massive than the Sun explode as supernovae at the end of their lives. The explosions, which leave behind a black hole or a neutron star, are so energetic they can outshine their host galaxies for months. However, astronomers appear to have spotted a massive star that skipped the explosion and turned directly into a black hole.
About half a century ago, astronomers theorized that the Solar System is situated in a low-density hot gas environment. This hot gas emits soft X-rays that displace the dust in the local interstellar medium (ISM), creating what is known as the Local Hot Bubble (LHB). This theory arose to explain the ubiquitous soft X-ray background (below 0.2 keV) and the lack of dust in our cosmic neighborhood. This theory has faced some challenges over the years, including the discovery that solar wind and neutral atoms interact with the heliosphere, leading to similar emissions of soft X-rays.
The dividing line between stars and planets is that stars have enough mass to fuse hydrogen into helium to produce their own light, while planets aren’t massive enough to produce core fusion. It’s generally a good way to divide them, except for brown dwarfs. These are bodies with a mass of about 15–80 Jupiters, so they are large enough to fuse deuterium but can’t generate helium. Another way to distinguish planets and stars is how they form. Stars form by the gravitational collapse of gas and dust within a molecular cloud, which allows them to gather mass on a short cosmic timescale. Planets, on the other hand, form by the gradual accumulation of gas and dust within the accretion disk of a young star. But again, that line becomes fuzzy for brown dwarfs.
Mars’ ancient climate is one of our Solar System’s most perplexing mysteries. The planet was once wet and warm; now it’s dry and cold. Whatever befell the planet, it didn’t happen all at once.
Space debris, which consists of pieces of spent rocket stages, satellites, and other objects launched into orbit since 1957 – is a growing concern. According to the ESA Space Debris Office, there are roughly 40,500 objects in LEO larger than 10 cm (3.9 inches) in diameter, an additional 1.1 million objects measuring 1 and 10 cm (0.39 to 3.9 inches) in diameter, and 130 million objects 1 mm to 1 cm (0.039 to 0.39 inches). The situation is projected to worsen as commercial space companies continue to deploy “mega-constellations” of satellites for research, telecommunications, and broadband internet services.
If I ask you to picture a radio telescope, you probably imagine a large dish pointing to the sky, or even an array of dish antennas such as the Very Large Array. What you likely don’t imagine is something that resembles a TV dish in your neighbor’s backyard. With modern electronics, it is relatively easy to build your own radio telescope. To understand out how it can be done, check out a recent paper by Jack Phelps.
The Hubble Space Telescope was carried to space inside the space shuttle Discovery and then released into low-Earth orbit. The James Webb Space Telescope was squeezed inside the nose cone of an Ariane 5 rocket and then launched. It deployed its mirror and shade on its way to its home at the Sun-Earth L2 Lagrange point.
In 1963, the Arecibo Observatory became operational on the island of Puerto Rico. Measuring 305 meters (~1000 ft) in diameter, Arecibo’s spherical reflector dish was the largest radio telescope in the world at the time – a record it maintained until 2016 with the construction of the Five-hundred-meter Aperture Spherical Telescope (FAST) in China. In December 2020, Arecibo’s reflector dish collapsed after some of its support cables snapped, leading the National Science Foundation (NSF) to decommission the Observatory.
Black holes are real. We see them throughout the cosmos, and have even directly imaged the supermassive black hole in M87 and our own Milky Way. We understand black holes quite well, but the theoretical descriptions of these cosmic creatures still have nagging issues. Perhaps the most famous issue is that of the singularity. According to the classical model of general relativity, all the matter that forms a black hole must be compressed into an infinite density, enclosed within a sphere of zero volume. We assume that somehow quantum physics will avert this problem, though without a theory of quantum gravity, we aren’t sure how. But the singularity isn’t the only infinite problem. Take, for example, the strange boundary known as the Cauchy horizon.
When we think of exoplanets that may be able to support life, we hone in on the habitable zone. A habitable zone is a region around a star where planets receive enough stellar energy to have liquid surface water. It’s a somewhat crude but helpful first step when examining thousands of exoplanets.
Nine years ago, Blue Origin revealed the plans for their New Glenn rocket, a heavy-lift vehicle with a reusable first stage that would compete with SpaceX for orbital flights. Since that time, SpaceX has launched hundreds of rockets, while Blue Origin has been working mostly in secret on New Glenn. Last week, the company rolled out the first prototype of the first-stage booster to the launch complex at Cape Canaveral Space Force Station. If all goes well, we could see a late November test on the launch pad.
One thing we’ve learned in recent decades is that exoplanets are surprisingly common. So far, we’ve confirmed nearly 6,000 planets, and we have evidence for thousands more. Most of these planets were discovered using the transit method. though we there are other methods as well. Many stars are known to have multiple planets, such as the TRAPPIST-1 system with seven Earth-sized worlds. But even within known planetary systems there could be planets we’ve overlooked. Perhaps their orbit doesn’t pass in front of the star from our vantage point, or the evidence of their presence is buried in data noise. How might we find them? A recent paper on the arXiv has an interesting approach.
Many people think of the James Webb Space Telescope as a sort of Hubble 2. They understand that the Hubble Space Telescope (HST) has served us well but is now old, and overdue for replacement. NASA seems to agree, as they have not sent a maintenance mission in over fifteen years, and are already preparing to wind down operations. But a recent paper argues that this is a mistake. Despite its age, HST still performs extremely well and continues to produce an avalanche of valuable scientific results. And given that JWST was never designed as a replacement for HST — it is an infrared (IR) telescope) — we would best be served by operating both telescopes in tandem, to maximize coverage of all observations.
On November 26th, 2018, NASA’s Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport (InSight) mission landed on Mars. This was a major milestone in Mars exploration since it was the first time a research station had been deployed to the surface to probe the planet’s interior. One of the most important instruments InSight would use to do this was the Heat Flow and Physical Properties Package (HP3) developed by the German Aerospace Center (DLR). Also known as the Martian Mole, this instrument measured the heat flow from deep inside the planet for four years.
The gravitational field of a rotating black hole is powerful and strange. It is so powerful that it warps space and time back upon itself, and it is so strange that even simple concepts such as motion and rotation are turned on their heads. Understanding how these concepts play out is challenging, but they help astronomers understand how black holes generate such tremendous energy. Take, for example, the concept of frame dragging.
According to the United Nations, the world produces about 430 million metric tons (267 U.S. tons) of plastic annually, two-thirds of which are only used for a short time and quickly become garbage. What’s more, plastics are the most harmful and persistent fraction of marine litter, accounting for at least 85% of total marine waste. This problem is easily recognizable due to the Great Pacific Garbage Patch and the amount of plastic waste that washes up on beaches and shores every year. Unless measures are taken to address this problem, the annual flow of plastic into the ocean could triple by 2040.
Space-based telescopes are remarkable. Their view isn’t obscured by the weather in our atmosphere, and so they can capture incredibly detailed images of the heavens. Unfortunately, they are quite limited in mirror size. As amazing as the James Webb Space Telescope is, its primary mirror is only 6.5 meters in diameter. Even then, the mirror had to have foldable components to fit into the launch rocket. In contrast, the Extremely Large Telescope currently under construction in northern Chile will have a mirror more than 39 meters across. If only we could launch such a large mirror into space! A new study looks at how that might be done.
Voyager 1 was launched waaaaaay back in 1977. I would have been 4 years old then! It’s an incredible achievement that technology that was built THAT long ago is still working. Yet here we are in 2024, Voyager 1 and 2 are getting older. Earlier this week, NASA had to turn off one of the radio transmitters on Voyager 1. This forced communication to rely upon the low-power radio. Alas technology around 50 years old does sometimes glitch and this was the result of a command to turn on a heater. The result was that Voyager 1 tripped into fault protection mode and switch communications! Oops.
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