Now We Know Why Pluto has These Strange Features on its Surface

In the center left of Pluto’s vast heart-shaped feature – informally named “Tombaugh Regio” - lies a vast, craterless plain that appears to be no more than 100 million years old, and is possibly still being shaped by geologic processes. This frozen region is north of Pluto’s icy mountains and has been informally named Sputnik Planum (Sputnik Plain), after Earth’s first artificial satellite. The surface appears to be divided into irregularly-shaped segments that are ringed by narrow troughs. Features that appear to be groups of mounds and fields of small pits are also visible. This image was acquired by the Long Range Reconnaissance Imager (LORRI) on July 14 from a distance of 48,000 miles (77,000 kilometers). Features as small as one-half mile (1 kilometer) across are visible. The blocky appearance of some features is due to compression of the image. Credits: NASA/JHUAPL/SWRI

After New Horizons made its close flyby of Pluto in July of 2015, scientists were astounded at the incredible closeup views of Pluto’s surface. One of the most intriguing and mysterious features was a bright plain inside the prominent heart-shaped feature on Pluto, called “Tombaugh Regio” (Tombaugh Region) named after Clyde Tombaugh, who discovered Pluto in 1930.

The region is composed of a broken surface of irregularly-shaped segments that appear to be geologically young because no impact craters are part of the terrain.

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Once New Horizons was out Beyond Pluto, it Could Finally Measure the Brightness of the Milky Way

This false-color map shows several scans of the Lyman-alpha background over the sky, obtained by the Alice ultraviolet spectrograph on the New Horizons spacecraft when it was 45 AU from the Sun. The data agrees well with an underlying model of the solar component of the Lyman-alpha background to which a constant brightness from the Milky Way has been added. The background is brighter at both directions near our Sun, which is marked here by an orange dot. Credit: SwRI

The New Horizons spacecraft has been speeding away from Earth since it launched in 2006. Scientists using the Alice UV imaging spectrograph on board New Horizons, have been patiently but sporadically gathering data during those 15 years, but also waiting to get far enough away from the Sun to make a specific measurement: the brightness of the Lyman-alpha background of the Milky Way. Until now, this had never been measured accurately.

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New Horizons is Now 50 Astronomical Units Away From the Sun

Currently exploring the Kuiper Belt, New Horizons is just one of five spacecraft to reach beyond 50 astronomical units, on its way out of the solar system and, eventually, into interstellar space. (Credit: NASA/Johns Hopkins APL/Southwest Research Institute)

As the New Horizons spacecraft hurtles out towards interstellar space, it has now reached an historical milestone. On April 17, 2021, New Horizons passed 50 astronomical units, or 50 times Earth’s distance from the Sun. It is just the 5th spacecraft to reach that distance, joining the Voyagers 1 and 2 and the Pioneers 10 and 11.

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Away From the Light Pollution of the Inner Solar System, New Horizons was Able to see how Dark the Universe Really is

NASA's New Horizons spacecraft (when it still lived on the Earth).

Just how dark is the universe, anyway? It’s a pretty hard thing to measure when we’re sitting this close to the sun. But NASA’s New Horizons probe is so far away that the images it takes of the distant universe are able to deliver the most accurate measurement ever of the universe’s diffuse background light.

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New Horizons Saw the Universe With Even Less Light Pollution than Hubble’s View

Artist's impression of New Horizons' close encounter with the Pluto–Charon system. Credit: NASA/JHU APL/SwRI/Steve Gribben

In July of 2015, NASA’s New Horizons probe made history when it became the first mission ever to conduct a close flyby of Pluto. This was followed by the spacecraft making the first-ever encounter with a Kuiper Belt Object (KBO) – known as Arrokoth (aka. 2014 MU69) – on Dec.31st, 2018. In addition, its unique position in the outer Solar System has allowed astronomers to conduct rare and lucrative science operations.

This has included parallax measurements of Proxima Centauri and Wolf 359, the two closest stars to the Solar System. In addition, a team of astronomers led by the National Optical Astronomy Observatory (NOAO) and Southwest Research Institute (SwRI) used archival data from the probe’s Long Range Reconnaissance Imager (LORRI) to conduct measurements of the Cosmic Optical Background (COB).

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Pluto has Snowcapped Mountains, But Why?

On the left, the region of "Cthulhu" near the equator of Pluto and on the right, the Alps on Earth. Two identical landscapes, created by very different processes. Image Credit: © NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute © Thomas Pesquet / ESA

We can thank NASA’s New Horizons spacecraft for opening our eyes up to Pluto’s complexity. On July 14th, 2015, the spacecraft came within 12,500 km (7,800 mi) of the dwarf planet. During the flyby, New Horizons was able to characterize Pluto’s atmosphere and its surface.

Among the things New Horizons saw was a region of snowcapped mountains.

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New Horizons is so Far From Earth That the Positions of the Stars Look a Little Different From its Perspective

Credit: NASA/JHUAPL

In July of 2015, the New Horizons spacecraft made history when it became the first robotic explorer to conduct a flyby of Pluto. This was followed by another first, when the NASA mission conducted the first flyby of a Kuiper Belt Object (KBO) on December 31st, 2018 – which has since been named Arrokoth. Now, on the edge of the Solar System, New Horizons is still yielding some groundbreaking views of the cosmos.

For example, we here on Earth are used to thinking that the positions of the stars are “fixed”. In a sense, they are, since their positions and motions are relatively uniform when seen from our perspective. But a recent experiment conducted by the New Horizons team shows how familiar stars like Proxima Centauri and Wolf 359 (two of the closest stars in our neighbors) look different when viewed from the edge of the Solar System.

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There Are Winds Blowing On Pluto, Driven by Frozen Nitrogen

NASA's New Horizons spacecraft captured this image of Sputnik Planitia — a glacial expanse rich in nitrogen, carbon monoxide and methane ices — that forms the left lobe of a heart-shaped feature on Pluto’s surface. SwRI scientists studied the dwarf planet’s nitrogen and carbon monoxide composition to develop a new theory for its formation. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Earth and Pluto don’t have much in common. Earth is a vibrant, living world, whereas Pluto is cold, distant and lifeless. But one thing they do have in common is nitrogen. Earth’s atmosphere is about 78% nitrogen, and Pluto’s primary atmospheric constituent is also nitrogen, although the exact percentage is unclear.

On Pluto, where the surface temperature is about 42 Kelvin (-231 Celsius) most of that nitrogen is frozen. A new study says that Pluto’s frozen nitrogen drives the planet’s winds, and shapes its feature surfaces.

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New Horizon’s Flyby Target 2014 MU69 Gets its Official Name: Arrokoth

Rev. Nick Miles, of the Pamunkey Tribe, opens the 2014 MU69/Arrokoth naming ceremony at NASA Headquarters with a traditional Algonquian song. Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

On July 14th, 2015, the New Horizons made the first-ever flyby of Pluto. As if that wasn’t enough, the mission made history again with the flyby of the Kuiper Belt Object (KBO) 2014 MU69 on December 31st, 2018. This constituted the farthest encounter from Earth with a celestial object, which the team had nicknamed Ultima Thule – a mythical northern island beyond the borders of the known world in Medieval literature.

Unfortunately, this name has generated some controversy due to the fact that it is also the name white supremacists use to refer to a mythical homeland. So with the consent of the tribal elders and representatives of the Powhatan nations, the New Horizons’ team recommended a new name for the KBO. Henceforth, it will be known as “Arrokoth“, the word for “sky” in the Powhatan/Algonquian language.

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New Horizons Team Pieces Together the Best Images They Have of Pluto’s Far Side

New Horizon's July 2015 flyby of Pluto captured this iconic image of the heart-shaped region called Tombaugh Regio. Credit: NASA/JHUAPL/SwRI.

Pluto was discovered in 1930 by astronomer Clyde Tombaugh. For decades, not much detail was known about the erstwhile planet. We assumed it was a frozen, dormant world.

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