Featured Mauna Kea Observatory discovery

A scorching exoplanet is providing new insight into how giant gas planets such as Jupiter and Saturn form.

WASP-76b, located 634 light-years away, has a superheated atmosphere of 2,000 degrees Celsius (3,632 degrees Fahrenheit) and orbits its star 12 times closer than Mercury orbits the sun. These extreme conditions cause this gas giant to “puff” to a volume of six times that of Jupiter and also vaporizes elements that would normally form rocks, making these materials detectable in its atmosphere.

As a result, scientists using the Gemini North Telescope on Mauna Kea were able to detect 11 such rock-forming elements — the abundance of which was similar to both our sun and the exoplanet’s host star. This provides additional evidence that giant gas planets form in a way that is more similar to star formation — coalescing out of gas and dust in a protoplanetary disk — rather than the gradual accretion of dust, rocks and planetesimals that form rocky planets.

Special events

Supermoon: On July 3 the full moon will appear bigger and brighter than normal. This is due to the full moon occurring while the moon is at perigee, when it is closest to Earth. This event is often called a supermoon. Supermoons can be up to 15% brighter than an average full moon.

Lahaina noon: In the last couple of weeks of July, locations across Hawaii will witness an astronomical event unique to the tropics known here as Lahaina noon.

Lahaina noon occurs when the sun passes through the center of the sky at solar noon. These days are also called “zenith sun” or “no shadow days.” As the sun is exactly overhead, anything with smooth sides (such as a soda can) will not cast a shadow in the moment that this happens.

This event can be observed only in the tropics, between the latitudes of 23 degrees south and 23 degrees north.

At ‘Imiloa Astronomy Center, the mosaic “Voyage of the Navigator” is positioned exactly under our skylight. When Lahaina noon occurs, the skylight will perfectly illuminate the mosaic beneath.

Locations in the tropics experience two Lahaina noons a year, with the dates depending on the latitude. Hilo’s first Lahaina noon occurred May 18, and its second will take place July 24 at 12:26 p.m. In Honolulu the first Lahaina noon of the year occurred May 27, and the second one lands on July 16 at 12:37 p.m.

Evening observing

Two notable planets will stand out in the early evening sky through July.

At the beginning of the month, Venus and Mars will appear close to each other above the western horizon. As the month goes on, they will continue to accompany each other as they get closer to the horizon.

Venus will likely be the planet that is spotted first as it is the third-brightest object in the sky after the sun and full moon. This visibility has long given the planet the title “the evening star” (despite the fact that it is a planet). Venus appears so bright because its thick atmosphere reflects much of the light that comes to the planet from the sun.

Just above Venus will be the rusty red planet Mars. While Mars will be significantly fainter than Venus, it will still stand out with its distinctive reddish color.

Mars owes its famous red color to its soil, which has largely rusted due to extreme climate change in the form of a runaway icehouse effect; climate change also caused the planet’s oceans to freeze. Today Mars is a giant cold desert.

In our early evening hours, we will be able to view two of the navigational star families utilized by modern wayfinders. Kaiwikuamo‘o will stretch over our heads connecting the North Star, Hokupa‘a, to the Southern Cross, Hanaiakamalama. July will be the last month this year when we can see the Southern Cross in our early evening sky. At the same time, our summer starline, Manaiakalani, will rise in the eastern sky.

Views of the Milky Way are spectacular during the summer months in Hawaii. In the early evening, when we look toward the shape of Kamakaunuiamaui, also known as Maui’s Fishhook, we see an area of the Milky Way band commonly called “the bulge,” which refers to the central regions of the galaxy.

The entire Milky Way band is illuminated by the combined light of millions of stars, most of which are too far away for us to see without assistance. However, a small telescope or even a pair of binoculars will allow us to see a multitude of stars in the Milky Way band, especially on clear dark, moonless nights with little light pollution.

Morning observing

Early-bird stargazers will enjoy a very different perspective of the night sky.

Throughout July the sun will rise around 6 a.m., and the light of dawn will color our sky starting just before 5:30 a.m. During these early morning hours, the four gas giant planets of our solar system will stretch across the sky. Of the four gas giant planets, Jupiter and Saturn will be the easiest to spot as we can see them with the naked eye.

For the planets of Uranus and Neptune, you will need to know exactly where to look and use a very good pair of binoculars or a telescope.

To spot these planets, face toward the south at about 5 a.m. The bright planet Jupiter will stand out during the early morning hours rising in the southeast, while Saturn will be more toward the southwestern area of the sky.

To find Uranus with a telescope, look about halfway between Jupiter and the star cluster of Makali‘i (Pleiades). Neptune will be much more difficult to detect as it is fainter and not as near any convenient “landmarks” in the sky. To find Neptune, look about 65 degrees above due south.

July 2023 Skywatch by Honolulu Star-Advertiser

The ‘Imiloa Astronomy Center of Hawaii is a center for informal science education at the University of Hawaii at Hilo showcasing astronomy and Hawaiian culture as parallel journeys of human exploration.