H I and dust in the high latitude dark cloud L1642

The high latitude dark cloud L1642 in the 21 cm H I region was mapped using a 100 m radio telescope. A remarkable H I line broadening from 2.5 to 2.9 km/s is observed over a small area on the bright side of L1642, i.e., the side facing the galactic plane. Results are presented concerning the effects of the asymmetrical UV radiation field of OB stars on the H I gas and the very small dust grains associated with L1642

Merkkipaaluja ja episodeja observaattori Henrik Walbeckin elämästä

Jo 1700-luvun loppuvuosina Turun akatemia oli tehnyt Ruotsin kuninkaalle useita – hiekkaan valuneita – esityksiä observatorion perustamisesta. Kun Suomesta oli tullut autonominen suuriruhtinaskunta, Venäjän keisari ryhtyi monilla tavoin edistämään yliopiston asiaa. Keisarin suostumus yliopiston konsistorin esitykseen observatorion rakentamisesta ja observaattorin viran perustamisesta saatiin 200 vuotta sitten, 31. maaliskuuta 1817. Observaattorin virkaan nimitettiin 18.11.1817 Henrik Johan Walbeck (1793–1822).&nbsp

Suomen tähtitieteen historiaa ja kulttuurihistoriaa

Raimo Lehti & Tapio Markkanen: History of Astronomy in Finland 1828–1918. Societas Scientiarum Fennica, The History of Learning and Science in Finland 1828– 1918, Vol. 4b. Helsinki 2010

Turun akatemian uudisrakennus

Kirjoituksessani ”Merkkipaaluja ja episodeja ob­servaattori Henrik Walbeckin elämästä” (Tietees­sä tapahtuu 6/2017) sanottiin: ”Observatorio val­mistui 1819 ja tähtitieteestä tuli täten yliopiston ensimmäinen oman ’laitosrakennuksensa’ saanut tiede.” Tämän johdosta professori Pekka Pyykkö huomautti, että vanhan Turun akatemian Kemian laitos vihittiin käyttöönsä jo vuonna 1764

The spectral energy distribution of the scattered light from dark clouds

A dark cloud is exposed to the ambient radiation field of integrated starlight in the Galaxy. Scattering of starlight by the dust particles gives rise to a diffuse surface brightness of the dark nebula. The intensity and the spectrum of this diffuse radiation can be used to investigate, e.g., the scattering parameters of the dust, the optical thickness of the cloud, and as a probe of the ambient radiation field at the location of the cloud. An understanding of the scattering process is also a prerequisite for the isolation of broad spectral features due to fluorescence or to any other non-scattering origin of the diffuse light. Model calculations are presented for multiple scattering in a spherical cloud. These calculations show that the different spectral shapes of the observed diffuse light can be reproduced with standard dust parameters. The possibility to use the observed spectrum as a diagnostic tool for analyzing the thickness of the cloud and the dust particle is discussed

A New Era in Extragalactic Background Light Measurements: The Cosmic History of Accretion, Nucleosynthesis and Reionization

(Brief Summary) What is the total radiative content of the Universe since the epoch of recombination? The extragalactic background light (EBL) spectrum captures the redshifted energy released from the first stellar objects, protogalaxies, and galaxies throughout cosmic history. Yet, we have not determined the brightness of the extragalactic sky from UV/optical to far-infrared wavelengths with sufficient accuracy to establish the radiative content of the Universe to better than an order of magnitude. Among many science topics, an accurate measurement of the EBL spectrum from optical to far-IR wavelengths, will address: What is the total energy released by stellar nucleosynthesis over cosmic history? Was significant energy released by non-stellar processes? Is there a diffuse component to the EBL anywhere from optical to sub-millimeter? When did first stars appear and how luminous was the reionization epoch? Absolute optical to mid-IR EBL spectrum to an astrophysically interesting accuracy can be established by wide field imagingat a distance of 5 AU or above the ecliptic plane where the zodiacal foreground is reduced by more than two orders of magnitude.Comment: 7 pages; Science White Paper for the US Astro 2010-2020 Decadal Survey. If interested in further community-wide efforts on this topic please contact the first autho